So why do we put up these signs in other places? On Thursday, amid opposition from state education leaders, the Assembly Judiciary Committee heard testimony on Assembly Bill 148, which would allow concealed-weapons permit holders to carry at public college campuses and schools under some circumstances.

Since at least 1950, all but two public mass shootings in America have taken place where general citizens are banned from carrying guns. In Europe, there have been no exceptions. Every mass public shooting has occurred in a gun-free zone. And Europe is no stranger to mass shootings. It has been host to three of the six worst K-12 school shootings and by far the worst mass public shooting perpetrated by a single individual.

Killers often openly talk about their desire to attack where guns are banned. Last June, Elliot Rodger, who killed six people in Santa Barbara, Calif., explained his own choice. In his 141-page “Manifesto,” Rodger turned down targets because he worried that someone with a gun would cut short his killing spree.

That same month, Justin Bourque shot to death three people in Canada. His Facebook page made fun of gun bans, with pictures of defenseless victims explaining to killers that they weren’t allowed to have their guns. . . .